The invention generally relates to a method and apparatus for the separation of caked filtrate from a filter media used in plate filter systems. More specifically, the invention relates to the removal of filtrate accumulated on an elongated or continuous filter web used in horizontal plate filter systems.
Plate-type industrial liquid filters are used to filter recycling liquids such as lubricants, cleansers or other materials in various machining or other mechanical operations. Several plate filters are usually stacked vertically to handle large volumes of industrial liquids for filtering. Each plate filter includes an upper chamber and lower chamber with a portion of filter web disposed therebetween. Liquid is introduced into the upper chamber and filtered by the filter web as the liquid passes into the lower chamber. As filtrate accumulates on the filter web, the filter web becomes contaminated and must be replaced by fresh filter web.
The filter web, an elongated sheet of filter media such as polyester, paper or the like, is supplied on rolls and can be advanced through the plate filter in incremental steps each time contamination of a portion necessitates fresh filter media. To advance the filter web, the upper and lower chambers are separated thereby releasing the portion of the sheet of filter web between the plates so that a filter web extractor located downstream can pull the filter media through the plate filter until a fresh portion is advanced between the upper and lower chambers. The upper and lower chambers are then closed together on the fresh filter web and the filtering continues.
As fresh filler web is advanced into the plate filters, the contaminated portion of the web is pulled out. The filter web exits the plate filter with considerable filtrate disposed upon its upper surface forming a filter cake. Many environmental restrictions warrant the separation of the filter media and filter cake before disposal.
Conventionally, separation of the filter cake from the filter web is done by hand. Once the contaminated filter web is extracted from the system, the filter web is cut up and deposited into a collection receptacle. An operator is required to pull the elongated sheets of filter media web out of the collection receptacle, sometimes called a debris box, and manually dislodge the caked filtrate from the filter media. The filter web is commonly provided in rolled sheets approximately 41 inches wide. During the filtering process, hundreds of pounds of filtrate, such as diatomaceous earth, Fuller's earth with oil, or other particulate matter, can accumulate on a sheet of filter web. As a result, manual separation of the heavy filtrate cake from the filter web is physically dangerous to the operator and extremely time consuming.
In a effort to improve the process, mechanical means for separation of filtrate cake from filter media in plate filter systems have been developed. One example is the apparatus disclosed in U.S. Pat. No. 4,869,834 to Hudson. This patent discloses a method and device having a driven rewind spindle that pulls filter paper media and filtrate cake from the plate filter chambers around a cylindrical bar fixed at a position of 45.degree. to the filter paper travel path. As the filter media bends around this cylindrical bar, the filtrate cake is dislodged from the filter media and falls into a collection container. The filter media, now upside down after bending around the cylindrical bar, is rolled upon a rewind mechanism. When the rewinder is full, the paper media is either unwound or cut off. This device is disadvantageous for several reasons. The travel of the contaminated filter media around the cylindrical bar compromises the alignment of the filter media through the mechanism. Constant supervision of the operation of the apparatus is required to assure proper alignment and to make necessary adjustments. Additionally, some filtrate may fail to dislodge from the filter media as the media is inverted. Furthermore, as the filter media is wound up at the end of the travel path, the rewinding or manual cutting of the paper media is time consuming especially in systems with multiple stacked plate filter chambers in a vertical arrangement.